1. Field of the Invention
This invention relates to an output voltage control system for an electric generator and more particularly to an improvement in such system wherein, when the rotary shaft of the electric generator is connected to an engine or the like prime mover experiencing extremely severe fluctuations in r.p.m., the currents supplied to a pair of field windings are controlled in such a manner as to produce a substantially constant output voltage not only for a load subject to fluctuations but for a stationary (fixed) load.
2. Description of the Prior Art
Various different systems have been proposed for controlling the output voltage for the electric generator. One of such prior-art systems disclosed in an unidentified prepublication and put to practical usage extensively is shown herein in FIG. 1.
Referring to FIG. 1, an electric generator 1 has an output 2 to which is connected a stationary load 3.
The generator 1 has a rotary shaft having a rotor, not shown, which is connected to a power drive source, such as an engine, also not shown.
A rectifier 4 is connected to the output 2, and a portion of the d.c. voltage derived from the rectifier 2 is applied to a comparator-amplifier 6 to which a reference voltage is also supplied for comparison with the firstly stated voltage and a resulting control current is supplied to a field coil 7 of the electric generator 1.
The above described conventional output voltage control system for an electric generator operates in such a manner that the a.c. output obtained at the output 2 of the generator 1 is supplied to the stationary load 3 while it is also supplied to the comparator-amplifier 6 so that a control current proportionate to load fluctuations is supplied to the field coil 7 in such a manner that the output of the generator 1 is maintained at a substantially constant value despite load fluctuations.
The above described conventional control system is however inconvenient in that, although output voltage control can be made satisfactorily against load fluctuations, it is not possible to perform fine voltage control for a stationary load, for which a separate constant voltage circuit is required.